1. Field of the Invention
The present invention relates to: an optical information recording medium which utilizes both groove regions (i.e., guide grooves) and land regions (i.e., regions between grooves) as information tracks, the grooves and lands having been previously formed on the optical information recording medium; and an optical information recording/reproduction device for recording an information signal on the optical information recording medium.
2. Description of the Related Art
In recent years, there have been vigorous research and development activities for realizing optical information recording media for recording and reproducing information signals (e.g., video signals and audio signals) thereon. One example of such an optical information recording medium is an optical disk. A recordable optical disk includes guide grooves (hereinafter referred to as xe2x80x9cgroovesxe2x80x9d) previously engraved on a substrate, the grooves constituting information tracks. Any region between adjoining grooves is referred to as a xe2x80x9clandxe2x80x9d. Information signals can be recorded or reproduced on the optical disk by converging a laser light beam on the flat portions of grooves or lands.
In the case of common commercially-available optical disks, information signals are typically recorded on either grooves or lands. When information signals are recorded on the grooves, for example, the lands serve as guard bands for separating adjoining tracks defined by the grooves. In the case where information signals are recorded on the lands, the grooves serve as guard bands.
FIG. 9 is a magnified perspective view of a conventional optical disk having the above-mentioned structure. In FIG. 9, reference numeral 85 denotes a recording layer (which may be composed of a phase-change material, for example); 86 denotes a recording pit; 87 denotes a laser beam spot; 88, 90, and 92 denote guide grooves defining xe2x80x9cgroovesxe2x80x9d; 89 and 91 denote xe2x80x9clandsxe2x80x9d; 93 denotes a transparent substrate through which light enters. As seen from FIG. 9, grooves are made wider than lands in this exemplary conventional optical disk.
In an attempt to increase the recording capacity of the above conventional optical disk, the interspaces between tracks are shortened by narrowing the widths of the lands 89. However, a smaller interspace between tracks results in a larger diffraction angle of light reflected from the grooves. This results in a lower level of tracking error signal, which is employed to ensure accurate tracing of the beam spot 87 on the tracks.
Moreover, there is a limit to the increase in track density achieved by merely reducing land widths. However, reducing the groove widths might lower the amplitude of the reproduced signal due to thinner recording pits 86.
On the other hand, there are techniques for increasing the track density, such as that disclosed in Japanese Patent Publication No. 63-57859, according to which information signals are recorded on both grooves and lands.
FIG. 10 is a magnified perspective view of such an optical disk. In FIG. 10, reference numeral 85 denotes a recording layer; 86 denotes a recording pit; 87 denotes a laser beam spot; 93 denotes a transparent substrate; 94, 96, and 98 denote grooves; 95 and 97 denote lands.
As shown in FIG. 10, the grooves and the lands have substantially the same width. Pre-pits 99, which are formed for both grooves and lands, are engraved at the beginnings of sectors of both information tracks (i.e., groove and lands) as identification signals representing locational information on the optical disk.
In the above optical disk, the recording pits 86 are formed for both grooves and lands as shown in FIG. 10. Although the grooves have a period equal to the period of grooves in the optical disk shown in FIG. 9, each interspace between adjoining recording pit rows in FIG. 10 is half of that of the optical disk shown in FIG. 9. As a result, the optical disk in FIG. 10 has twice as large a recording capacity as that of the optical disk in FIG. 9.
Rewritable optical disks require identification signals (indicating location information on the disk), etc., to be previously recorded on the disk. The inventors of the present invention have proposed in Japanese Laid-Open Patent Publication No. 6-176404 a technique of recording one identification signal for an adjoining pair consisting of a groove and a land so as to be located between the groove and the land.
However, in the above-mentioned optical information recording media, the track pitch is reduced to half of that of conventional optical information recording media, thereby requiring an even more accurate track servo control. Particularly when an identification signal is recorded between a land and its corresponding groove, only one half of the beam spot will be incident on the pre-pits. Therefore, when the beam spot shifts away from the track center, toward regions where the identification signal is not present, it may be impossible to detect the identification signal.
An optical information recording medium according to the present invention includes at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, wherein the optical information recording medium further includes: an identification signal region including a pre-pit array, the pre-pit array indicating identification information concerning the groove track and the land track; and a servo control region disposed ahead of the identification signal region along the groove track and the land track, the servo control region including wobble pits positioned so as to shift to opposite sides of a center line of either the groove track or the land track.
In one embodiment of the invention, the wobble pits include a plurality of pairs of pre-pits positioned so as to shift to opposite sides of the center line.
In another embodiment of the invention, the plurality of pairs of pre-pits indicate a reproduction synchronization signal.
In still another embodiment of the invention, a synchronization signal section indicating the beginning of the wobble pits is provided immediately before the wobble pits, and the synchronization signal section includes a pit array positioned on the center line of either the groove track or the land track.
In still another embodiment of the invention, at least a portion of the pre-pit array in the identification signal region is formed so as to be shifted away from the center line of either the groove track or the land track.
In still another embodiment of the invention, the identification signal region includes a pit indicating a track identification signal.
In still another embodiment of the invention, the pit indicating the track identification signal is shifted away from the center line of either the groove track or the land track.
In still another embodiment of the invention, the groove track and the land track are divided into a plurality of sectors, the pre-pit array in the identification signal region includes an address pit array indicating address information of a corresponding sector.
In still another embodiment of the invention, the groove track and the land track are formed in a spiral or concentric shape on a disk substrate.
In still another embodiment of the invention, the identification information includes a track number.
In still another embodiment of the invention, a portion of the pre-pit array indicating the identification signal that indicates the track number is shifted away from the center line of either the groove track or the land track along a direction across the groove track and the land track.
In still another embodiment of the invention, pre-pits in the pre-pit array indicating the identification signal which are formed so as to be shifted away from the center line of either the groove track or the land track are shifted away from the center line of either the groove track or the land track by about xc2xc of a track pitch.
In still another embodiment of the invention, an optical depth or height of the pre-pit array indicating the identification signal is substantially equal to the depth of the groove track.
In still another embodiment of the invention, an optical depth or height of the pre-pit array indicating the identification signal is substantially equal to xcex/4 (where xcex represents the wavelength of a light beam)
In still another embodiment of the invention, the width of the pre-pit array indicating the identification signal is substantially equal to the width of the groove track.
In still another embodiment of the invention, the width of the pre-pit array in the synchronization signal or the pre-pit array indicating the identification signal is larger than the width of the groove track.
In still another embodiment of the invention, a gap section is provided between the servo control region and the identification signal region.
In still another embodiment of the invention, the optical information recording medium further includes a rewritable recording layer, wherein the recording layer is formed of a phase-change type material capable of taking an amorphous state or a crystal state.
In another aspect, the present invention provides an optical information recording/reproduction device for recording/reproducing information with a light beam on an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, and the optical information recording medium further including: an identification signal region including a pre-pit array, the pre-pit array indicating identification information concerning the groove track and the land track; and a servo control region disposed ahead of the identification signal region along the groove track and the land track, the servo control region including wobble pits positioned so as to shift to opposite sides of a center line of either the groove track or the land track, and the optical information recording/reproduction device including: an optical system for allowing the light beam emitted from a light source to be incident on the optical information recording medium; transportation means for moving the relative position of a light spot on the optical information recording medium created by the light beam along a direction in which the groove track and the land track extend; light detection means for receiving reflected light of the beam spot from the optical information recording medium in a plurality of light receiving portions and for converting the reflected light into an electric signal which is output as a light detection signal; identification signal reading means for reproducing the identification signal from the light detection signal; a first tracking error detection circuit for detecting, while the optical spot travels on the groove track or the land track, a shift amount of the optical spot with respect to the center line and for outputting a first error signal indicating the shift amount; a second tracking error detection circuit for detecting, while the optical spot is travelling over the servo control region, a shift amount of the optical spot with respect to the center line by detecting the intensity of returned light from the wobble pits and for outputting a second error signal indicating the shift amount; a correction circuit for outputting a tracking signal obtained by correcting the first error signal based on the second error signal; and a tracking controller for controlling the transportation means to cause the beam spot to travel over the groove track or the land track based on the tracking signal.
Alternatively, the present invention provides an optical information recording/reproduction device for recording/reproducing information with a light beam on an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, and the optical information recording medium further including: an identification signal region including a pre-pit array, the pre-pit array indicating identification information concerning the groove track and the land track; and a servo control region disposed ahead of the identification signal region along the groove track and the land track, the servo control region including wobble pits positioned so as to shift to opposite sides of a center line of either the groove track or the land track; and a synchronization signal section indicating the beginning of the wobble pits, the synchronization signal section being provided immediately before the wobble pits and including a pit array positioned on the center line of either the groove track or the land track, and the optical information recording/reproduction device including: an optical system for allowing the light beam emitted from a light source to be incident on the optical information recording medium; transportation means for moving the relative position of a light spot on the optical information recording medium created by the light beam along a direction in which the groove track and the land track extend; light detection means for receiving reflected light of the beam spot from the optical information recording medium in a plurality of light receiving portions and for converting the reflected light into an electric signal which is output as a light detection signal; identification signal reading means for reproducing the identification signal from the light detection signal; a first tracking error detection circuit for detecting, while the optical spot travels on the groove track or the land track, a shift amount of the optical spot with respect to the center line and for outputting a first error signal indicating the shift amount; synchronization signal detection means for detecting from the light detection signal a point in time at which the beam spot travels over the synchronization signal section and outputting a reference signal indicating the point in time; a second tracking error detection circuit for detecting, while the optical spot is travelling over the servo control region, a shift amount of the optical spot with respect to the center line based on the reference signal and the light detection signal and for outputting a second error signal indicating the shift amount; synthesizing means for outputting a tracking signal based on the first error signal and the second error signal; and a tracking controller for controlling the transportation means to cause the beam spot to travel over the groove track or the land track based on the tracking signal.
In one embodiment of the invention, the synthesizing means outputs a signal obtained by adding the second error signal to the first error signal as the third error signal.
In another embodiment of the invention, the synthesizing means includes: identification signal region detection means for detecting whether or not the beam spot is travelling over the identification signal region and outputting a region detection signal while the beam spot is travelling over the identification signal region; and error signal retention means for retaining the third error signal while the region detection signal is output.
In still another embodiment of the invention, the second tracking error detection means derives a difference between a d.c. component of the light detection signal obtained after the lapse of a first time interval from a point in time at which the reference signal is input and a d.c. component of the light detection signal obtained after the lapse of a second time interval from the point in time and generates the second error signal based on the difference.
In still another embodiment of the invention, the light detection means includes two light receiving portions disposed symmetrically with respect to a direction across the groove track and the land track, each light receiving portion converting a received light amount into an electric signal; the first tracking error detection means includes differential operation means for deriving a difference between the electric signals output from the two light receiving portions; and the second tracking error detection means includes addition operation means for deriving a sum of the electric signals output from the two light receiving portions; and
In still another embodiment of the invention, the optical information recording/reproduction device further includes: recording means for recording an information signal on the groove track or the land track; recording control means for controlling the recording means so as not to record the information signal in the identification signal region.
Alternatively, the present invention provides an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, wherein the optical information recording medium further includes: a pre-pit array indicating identification information concerning the groove track and the land track; and a plurality of pits disposed ahead of the pre-pit array along the groove track and the land track, the plurality of pits indicating a reproduction synchronization signal for reproducing the identification information of the pre-pit array, the plurality of pits indicating the reproduction synchronization signal being positioned so as to shift to opposite sides of a center line of either the groove track or the land track.
In one embodiment of the invention, the groove track and the land track are divided into a plurality of sectors, the pre-pit array in the identification signal region includes an address pit array indicating address information of a corresponding sector.
Alternatively, the present invention provides an optical information recording/reproduction device for recording/reproducing information with a light beam on an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, and the optical information recording medium further including: a pre-pit array indicating identification information concerning the groove track and the land track; and a plurality of pits disposed ahead of the pre-pit array along the groove track and the land track, the plurality of pits indicating a reproduction synchronization signal for reproducing the identification information of the pre-pit array, the plurality of pits indicating the reproduction synchronization signal being positioned so as to shift to opposite sides of a center line of either the groove track or the land track, wherein the optical information recording/reproduction device includes a circuit for correcting a tracking offset based on the plurality of pits indicating the reproduction synchronization signal.
Alternatively, the present invention provides an optical information recording medium including information tracks including at least one groove track and at least one land track formed in a spiral or concentric shape on a disk substrate, the optical information recording medium including at least one zone composed of a plurality of information tracks, wherein the optical information recording medium further includes: a servo control region defined by a meandering portion of the groove track, the meandering portion having at least one meander; an identification signal region including one pre-pit indicating an identification signal provided for a pair consisting of adjoining ones of the groove track and the land track, the center lines of some or all of the pre-pits being shifted away from the center line of either the groove track or the land track along a direction across the groove track and the land track; and an information signal region in which an information signal is recorded by irradiation of a light beam, the an information signal region being distinct from the identification signal region.
Alternatively, the present invention provides an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, the optical information recording medium further including: an identification signal region including a pre-pit array indicating identification information concerning the groove track and the land track; and an information signal region in which an information signal is recorded by irradiation of a light beam, wherein the pre-pit array indicating the identification signal includes: a field number pre-pit indicating a field number representing the order of information fields composed of a pair consisting of adjoining ones of the groove track and the land track; and a track identification pre-pit for detecting whether a beam spot created on the optical information recording medium by the light beam is currently travelling over the groove track or the land track, wherein the field number pre-pit is formed substantially on a border line between the groove track and the land track included in each information field, the field number pre-pit being provided with a period twice as large as a track pitch along a direction perpendicular to the groove track and the land track, and the track identification pre-pit is formed substantially on a border line between two adjoining information fields, the track identification pre-pit being provided with a period four as large as the track pitch along the direction perpendicular to the groove track and the land track.
In one embodiment of the invention, the track identification pre-pit includes: a first track identifier disposed on the same line as the field number pre-pit array; a second track identifier disposed ahead of the first track identifier along the track direction and located between the first track identifiers adjoining each other along the direction perpendicular to the groove track and the land track.
In another embodiment of the invention, the optical information recording medium further includes a rewritable recording layer, wherein the recording layer is formed of a phase-change type material capable of taking an amorphous state or a crystal state.
Alternatively, the present invention provides an optical information recording/reproduction device for recording/reproducing information with a light beam on an optical information recording medium including at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other, the optical information recording medium further including: an identification signal region including a pre-pit array indicating identification information concerning the groove track and the land track; and an information signal region in which an information signal is recorded by irradiation of a light beam, wherein the pre-pit array indicating the identification signal includes: a field number pre-pit indicating a field number representing the order of information fields composed of a pair consisting of adjoining ones of the groove track and the land track; and a track identification pre-pit for detecting whether a beam spot created on the optical information recording medium by the light beam is currently travelling over the groove track or the land track, wherein the field number pre-pit is formed substantially on a border line between the groove track and the land track included in each information field, the field number pre-pit being provided with a period twice as large as a track pitch along a direction perpendicular to the groove track and the land track, and the track identification pre-pit is formed substantially on a border line between two adjoining information fields, the track identification pre-pit being provided with a period four as large as the track pitch along the direction perpendicular to the groove track and the land track, wherein the optical information recording/reproduction device includes: an optical system for allowing the light beam emitted from a light source to be incident on the optical information recording medium; light detection means for receiving the light beam reflected from the optical information recording medium and converting the reflected light into an electric signal which is output as a light detection signal; identification signal reading means for reproducing the identification signal from the light detection signal and outputting at least the field number; and track identifier detection means for outputting an identifier detection signal in the case where a signal from the track identification pre-pit is detected.
Thus, the invention described herein makes possible the advantages of: (1) providing an optical information recording medium utilizing information tracks composed of grooves and lands previously formed on the optical information recording medium, which does not require an unduly high accuracy of track serve control; and (2) providing an optical information recording/reproduction device for recording an information signal on such an optical information recording medium.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.